Description
Overview
This is a short set of practice problems involving writing loops and using arrays. You will write eight
methods for the class LoopsAndArrays. All of the methods are static, so your class will not have any
instance variables (or any static variables, for that matter). There is a constructor, but it is declared private
so the class cannot be instantiated.
For details and examples see the online javadoc.
My Code’s Not Working!
Developing loops can be hard. If you are getting errors, a good idea is to take a simple concrete example,
and trace execution of your code by hand (as illustrated in section 6.2 of the text) to see if the code is doing
what you want it to do. You can also trace what’s happening in the code by temporarily inserting println
statements to check whether variables are getting updated in the way you expect. (Remember to remove the
extra println’s when you’re done!)
Overall, the best way to trace through code with the debugger, as we are practicing in Lab 6. Learn to
use the debugger effectively, and it will be a lifelong friend.
Always remember: one of the wonderful things about programming is that within the world of your own
code, you have absolute, godlike power. If the code isn’t doing what you want it to do, you can decide what
you really want, and make it so. You are in complete control! (If you are not sure what you want the code
to do, well, that’s a different problem. Go back to the ”Advice” section.)
Specification
The specification for this assignment includes this pdf, the LoopsAndArrays javadocs, along with any “official” clarifications posted on Piazza.
Where’s the main() method??
There isn’t one! Like most Java classes, this isn’t a complete program and you can’t “run” it by itself. It’s
just a single class, that is, the definition for a type of object that might be part of a larger system. To try out
your class, you can write a test class with a main method.
There will also be a SpecChecker (not ready yet) that will perform a lot of functional tests, but when
you are developing and debugging your code at first you’ll always want to have some simple test cases of
your own as in the main method above.
Note that neither the SpecChecker nor the provided test program nor the combination of the pair provide
complete, comprehensive test coverage of your implementation. You will have to write your own tests.
Sample usage
A good way to think about the specification is to try to write some simple test cases and think about what
behavior you expect to see.
There is also a SpecChecker (see below) that will perform a lot of functional tests, but when you are
developing and debugging your code at first you’ll always want to have some simple test cases of your own.
Suggestions for getting started
Smart developers don’t try to write all the code and then try to find dozens of errors all at once; they work
incrementally and test every new feature as it’s written. Here is a rough guide for how an experienced coder
might go about creating a class such as this one:
• Create a new, empty project and add a package called mini1.
• Create the LoopsAndArrays class in the mini1 package and put in stubs for all the required methods.
For methods that are required to return a value, just put in a “dummy” return statement that returns
zero or false.
• Download the specchecker, import it into your project as you did in labs 1 and 2, and run it. There will
be lots of error messages appearing in the console output, since you haven’t actually implemented the
methods yet. Always start reading from the top. All you really want to check at this point is whether
you have a missing or extra public method, if the method declarations are incorrect, or if something
is really wrong like the class having the incorrect name or package. Any such errors will appear first
in the output and will usually say “Class does not conform to specification.”
• Before you write code for a method, always write a simple usage example or test case. This will make
sure you understand what the code is really supposed to do, and it will give later you a way to check
whether you did it correctly. Of course, if you are really not sure what a method is supposed to do,
bring up your question for discussion on Piazza!
The SpecChecker
You can find the SpecChecker online; see the Piazza Homework post for the link. Import and run the
SpecChecker just as you practiced in Labs 1 and 2. It will run a number of functional tests and then bring
up a dialog offering to create a zip file to submit. Remember that error messages will appear in the console
output. There are many test cases so there may be an overwhelming number of error messages. Always start
reading the errors at the top and make incremental corrections in the code to fix them. When you are happy
with your results, click “Yes” at the dialog to create the zip file. See the document “SpecChecker HOWTO”,
which can be found in the Piazza pinned messages
More about grading
This is a miniassignment and the grading is automated. If you do not submit it correctly, you will receive at
most half credit.
If you have questions
For questions, please see the Piazza Q & A pages and click on the folder miniassignment1. If you don’t
find your question answered, then create a new post with your question. Try to state the question or topic
clearly in the title of your post, and attach the tag miniassignment1. But remember, do not post any source
code for the classes that are to be turned in. It is fine to post source code for general Java examples that are
not being turned in. (In the Piazza editor, use the button labeled “pre” to have Java code formatted the way
you typed it.)
If you have a question that absolutely cannot be asked without showing part of your source code, make
the post “private” so that only the instructors and TAs can see it. Be sure you have stated a specific question;
vague requests of the form “read all my code and tell me what’s wrong with it” will generally be ignored.
Of course, the instructors and TAs are always available to help you. See the Office Hours section of the
syllabus to find a time that is convenient for you. We do our best to answer every question carefully, short
of actually writing your code for you, but it would be unfair for the staff to fully review your assignment in
detail before it is turned in.
Any posts from the instructors on Piazza that are labeled “Official Clarification” are considered to be
part of the spec, and you may lose points if you ignore them. Such posts will always be placed in the
Announcements section of the course page in addition to the Q & A page. (We promise that no official
clarifications will be posted within 24 hours of the due date.)
What to turn in
Please submit, on Canvas, the zip file that is created by the SpecChecker. The file will be named SUBMIT THIS mini1.zip. and it will be located in the directory you selected when you ran the SpecChecker. It
should contain one directory, mini1, which in turn contains one file, LoopsAndArrays.java. Always LOOK
in the zip file the file to check what you have submitted! Submit the zip file to Canvas using the Miniassignment1 submission link and verify that your submission was successful. If you are not sure how to do this,
see the document ”Assignment Submission HOWTO” which can be found in the Piazza pinned messages
under Syllabus, office hours, useful links.
We strongly recommend that you just submit the zip file created by the specchecker. If you mess something up and we have to run your code manually, you will receive at most half the points. If necessary for
some reason, you can create a zip file yourself. The zip file must contain the directory mini1, which in turn
should contain the file LoopsAndArrays.java. You can accomplish this by zipping up the src directory of
your project. The file must be a zip file, so be sure you are using the Windows or Mac zip utility, and not a
third-party installation of WinRAR, 7-zip, or Winzip.
